1. Field of the Invention
This invention relates to manipulators for handling heavy workpieces undergoing forging operations.
2. Description of the Prior Art
In order to manipulate heavy forged pieces, forging manipulators are used whose gripper which holds the forged piece is adapted for raising, lowering, horizontal and vertical pivoting, lateral parallel displacement, turning and axial movement. For this purpose known forging manipulators are provided with bearings supported in a travelling frame or carriage by connecting rods for a gripper carrier which is rotatable in the bearings. The connecting rods are telescopic piston-cylinder units connected by a ball-and-socket joint at one end to vertically displaceably forks pivotable in the travelling frame and at the other and to cross arms supporting the bearings of the gripper carrier, the gripper carrier with its bearings being horizontally displaceable on the cross arms. The design of the telescopic connecting rods, which are formed by integrated piston-cylinder units and which with the pair of connecting rods adjacent the gripper head are adapted for vertical springing and with the rear pair of connecting rods are adapted for setting the inclination of the gripper carrier, in order to prevent excessive loading of the bearings and to ensure movement of the forged piece between the forging tools of the press without contact or with slight thrust pressure, has resulted in the cross arms which support the gripper carrier with its bearings being arranged below the bearings (West German Patent No. DE-PS 22 55009, corresponding to British Patent Specification No. 1,410,696). An advantage of this arrangement is also that relatively long connecting rods are involved, so that their angles of deflection remain small during a predetermined longitudinal or transverse movement of the gripper carrier (West German Patent No. DE-PS 12 98 497 corresponding to U.S. Pat. No. 3,498,490).
On account of the saddle height of the lower forging tool, it should be possible for the gripper carrier to be lowered as closely as possible to the shop floor in its lower position and if the distance from the shop floor to the center of the gripper carrier is not sufficient for receiving the bearings with the associated cross arm, the bearings and the cross arm have been moved towards one another in the direction of the axis of the gripper carrier, with the disadvantage that the housing receiving the bearings of the gripper carrier and connecting the latter is subject to the bending moments which result from the bearing pressures and the displacement of the cross arm towards the bearings.